The sun is the source of phenomena in the solar terrestrial space environment, and ground-based solar observations have important scientific and educational value. The optical telescope is an effective observation equipment. This article introduces the construction ideas and methods of an optical telescope teaching experimental system, which has three functions: star searching and guidance, sun observation, and night sky photography. In response to the teaching needs of the course, 11 experiments were conducted, including observations of the solar sphere and chromosphere, imaging observations of the moon, observations of major planets (Saturn, Jupiter, or Mars) and imaging observations of galaxies, effectively improving the practical teaching effectiveness of the course.
Free space laser communication has the characteristics of large bandwidth, high speed, high security and small size, and has become the preferred way of high-speed data transmission in space today. The realization of multi-beam control in free-space optical communication through optical phased array has obvious advantages in energy consumption and control accuracy. Gerchberg-Saxton (GS) is a commonly used modulation phase design method for optical phased arrays. This paper analyzes the relationship between the beam efficiency and accuracy and the number of iterations in the modulation phase of optical phased arrays designed by the GS algorithm. The results show that in the ideal case, the beam efficiency increases with the number of iterations of the GS algorithm, and eventually tends to be stable; the beam pointing accuracy increases with the number of iterations of the GS algorithm, and finally tends to be stable, and the speed of stable convergence is faster than the beam efficiency.
KEYWORDS: Tissues, Brain-machine interfaces, Data modeling, Dielectrics, Electrodes, Signal attenuation, Data acquisition, Statistical analysis, Signal generators, Data communications
In recent years, wireless body area networks have developed ubiquitously and universally. The technology of using the human body as a communication medium to communicate through capacitive coupling has become a research hotspot. In order to explore the transmission characteristics of human body communication with different body mass indexes, this paper is based on the FDTD method, using homogeneous and inhomogeneous tissue human body models to simulate human body communication channels with different body mass indexes. It can be drawn from the simulation results that the loss of human body communication on the surface increases with the increase of the transmission distance. At the same time, in vivo experiments were carried out with reference to the simulation model. We used Maximum Likelihood Estimation (MLE) and Akaike Information Criterion (AIC) to analyse the normalized received power, and then used different fading models to perform statistical analysis on it. At 50MHz operating frequency, the channel loss increased with distance, and the increase in body index would reduce transmission loss. Comparing simulation and measurement results, we found that the attenuation trends of the two are not consistent. Through measurement and transmission of ASK data, the average BER of surface human body communication was ≤10-8, which verified that the higher BMI, the better performance of the human body communication channels. Based on the above results, this paper initially verified the feasibility and individual differences of the surface human body communication channels to transmit information.
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